Cherry Fruit Worm: Appearance, Territory, Damage and Life Cycle

Latin Name: Grapholita Packardi

Appearance: In British Columbia, Cherry Fruitworm is an occasional pest of blueberry crops. It was originally reported that it was causing blueberry fruit infestation in one site. Larvae consume growing fruit and contaminate it with frass and webbing. Adults are tiny, dark gray/brownish moths with 9-10 mm wingspan. They are usually active at night and hence are rarely observed. The bodies of the larvae are pink-red, with brown or black heads. Larvae that have just hatched tunnel inside fruit. A single larva may quickly consume an entire cluster of fruit.

Hosts Plants: Sweet and sour cherries and blueberries are the primary hosts; wild hosts include bitter cherry/wild cherry and chokecherry; other reported hosts include apple, hawthorn, plums, peaches, pears, roses, and quince.

Territory: Cherry fruitworm is a native North American fruit insect that is a prominent problem in eastern blueberry growing areas such as Michigan. Because of its biology, it is tough to govern.

Damage Insect Cause: Infested fruit is difficult to detect since there is little outward sign of the insect’s presence. Larvae are well-hidden inside berries that have been silked together tightly yet inconspicuously. Look for a pin-sized entrance hole near the stem of any tiny berries that have turned blue, and then open nearby berries to locate the scarlet larva. Often, the only obvious evidence of an infestation is a premature color change in the fruit. Larvae burrow into green fruit, contaminating it with frass and leaving an entry and/or exit hole in the berry’s cheek. Because there is little shriveling or softness, infested fruit cannot be thoroughly sorted out on the processing line or during harvesting.

Life History and Habits: Each year, the cherry fruit worm produces one generation. Moths emerge in the spring (late May to early June), mate, and lay their eggs on green fruit. Larvae hatch and burrow inside fruit as it develops. Young larvae eat within the calyx end of the fruit. Frass pellets remain within the fruit and are not visible from the outside. In early to mid-August, larvae will infest roughly two fruits before departing and looking for an overwintering place. At this time of year, pink larvae can be spotted crawling on picking flats. When the larvae leave the fruit in early August, the frass persists. Larvae construct a silken framework and spend the winter as pre-pupae in pruning stubs, wounds, or beneath the bark on tree trunks. Larvae pupate in the spring (April-May).